Various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending applications filed by the Applicant or Assignee of the present invention on 23 May 2000:
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In addition, various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending U.S. patent applications filed simultaneously by the applicant or assignee of the present invention: Ser. No. 09/607,985, U.S. Pat. No. 6,398,332, 6,394,573.
The disclosures of these co-pending applications are incorporated herein by cross-reference. Each application is temporarily identified by its docket number, which will be replaced by the corresponding USSN when available.
Of particular relevance is U.S. patent application entitled “Printed Page Tag Encoder”, hereafter referred to by reference docket No. 09/575,109.
Nowadays, nearly every item purchased from a shop contains a barcode of some description on the packaging. The barcode provides a convenient way of identifying an object by a product number. The exact interpretation of the product number depends on the type of barcode. Warehouse inventory tracking systems let users define their own product number ranges, while inventories in shops must be more universally encoded so that products from one company don't overlap with products from another company.
Barcodes themselves have been specified in a large number of formats. The older barcode formats contain characters that are displayed in the form of lines. The combination of black and white lines describe the information the barcodes contains. Often there are two types of lines to form the complete barcode: the characters (the information itself) and lines to separate blocks for better optical recognition. While the information may change from barcode to barcode, the lines to separate blocks stay constant. The lines to separate blocks can therefore be thought of as part of the constant structural components of the barcode.
Barcodes are read with specialized reading devices, such as lightpens, gun readers and scanners, that pass the extracted data onto a computer for further processing.
To help ensure that the extracted data was read correctly, checksums were introduced as a crude form of error detection. More recent barcode formats use redundancy encoding schemes such as Reed-Solomon. Such a scheme is utilized in the Aztec 2D barcode as disclosed U.S. Pat. No. 5,591,956. Often the degree of redundancy encoding is user selectable.
Two dimensional barcodes have been developed in which the information is encoded in two dimensions, instead of storing the information as a series of lines where the data is extracted from a single dimension. Just as with the original barcodes, the 2D barcode contains both information and structural components for better optical recognition. FIG. 1 shows an example of a Quick Response (QR) Code, developed by Denso of Japan and disclosed in U.S. Pat. No. 5,726,435. Note the barcode cell is comprised of two areas: a data area (depending on the data being stored in the barcode), and a constant position detection pattern. The constant position detection pattern is used by the reader to help locate the cell itself, then to locate the cell boundaries, to allow the reader to determine the original orientation of the cell. The orientation can be determined by the fact that there is no 4th corner pattern.
One problem associated with the range of barcodes available is that hardware for producing these barcodes is specific to the particular barcode format. As printers become more and more embedded, there is an increasing desire for real-time printing of these barcodes.